The airspace is divided into different layers depending on the height and proximity to an airport. The airspace closest to an airport is known as controlled airspace at all heights from the ground up to 46 000 feet. The main principle is that outside the airport area, only the higher levels, 10 000 feet to 46 000 feet, is controlled airspace – the rest is free airspace. In controlled airspace LFV´s air traffic controllers guides the aircrafts through radar and radio contact with the pilots. LFV´s controller ensures that the aircrafts are managed in an efficient and safe manner. In uncontrolled airspace, it is allowed to fly without contact with the air traffic controllers (although there are safety rules even there). This means that, for example, small aircrafts and helicopters often fly in uncontrolled airspace without contact with air traffic controllers. Passenger plane, however, is always flying in controlled airspace. Designing airspace and air routes is complex. In the development of routes, several factors must be considered from the financial, capacity, safety and environmental perspective.